1. Field of the Invention
The present invention relates generally to a control apparatus for the automatic embroidery sewing machine, and more particularly to an improvement in and to the control system for use in the embroidering sewing machine which provides control facilities permitting the automatic embroidering operations to be continued finally to reproduce an exact copy as a whole of a selected embroidery design or figure on a fabric ground. The control facilities are provided such that if the driving mechanism for supporting and moving the frame which carries a fabric ground to be embroidered does not cause the frame actually to be moved in a quantity of travel equivalent to the controlled quantity represented by an output signal from the control system for each stitch operation provided by the sewing machine, the difference between the actual travel and controlled travel quantities is added for correction to a controlled quantity of travel for the next succeeding stitch operation, thereby making the original design as a whole exactly to be copied on the fabric ground.
2. Description of the Prior Art
In a typical embroidery sewing machine known in the prior art, two servomotors are controlled in accordance with a programmed control data sequence which represents quantities of travel in x- and y-axis directions for the driving mechanism which supports and drives a cloth carrying frame to travel in accordance with the programmed design. The control data program is stored in the memory element in the control circuitry arrangement, and controls the two servomotors to provide their respective output powers which are combined into a plane pattern representing a resultant composed motion of x and y co-ordinate component motions. Thus, the driving mechanism is moved in accordance with the plane pattern in synchronized relationships with each up and down movement of a needle for each stitching operation provided by the sewing machine, so that the cloth frame carried and driven by the driving mechanism can be continually moved following a programmed plane pattern path.
In the prior art sewing machine, if a D.C. servomotor is employed as a power source for the frame driving mechanism, and is operated by feedback control signals provided by the control circuitry, the driving torque supplied by the servomotor may often be attenuated to be equal to the load near the end of each stitch control operation. Therefore, the servomotor may still remain on rotation until completion of the quantity of travel equivalent to the controlled quantity of travel for the appropriate stitch operation, and in this state may receive a new stitch timing which permits the frame to be driven for the next stitch operation. This may be a sort of malfunction or incomplete operation of the servomotor, and if the frame driving operations are continued by such servomotor in this situation in accordance with the programmed control data read out from the memory element, the thus obtained product carries an irregularly deformed copy of the desired original pattern.
Another typical embroidery sewing machine is known in the prior art, which provides indicator means which permits an applique needle work as well as ordinary embroidery needle work. This sewing machine provides automatic embroidery control functions which are performed in accordance with a programmed embroidery control data sequence stored in memory through the appropriate data entry means, so that the driving mechanism for supporting and driving the fabric ground carrying frame can be operated under program control. In this prior art sewing machine, an applique needle work can be performed in accordance with a control data sequence which is specifically programmed to meet the applique working requirements. However, the sewing machine provides no switching capabilities between the applique attachement cloth needle work and the fabric ground embroidering work. This may require a careful attention on the part of the machine operator on switching to another operation, in order to ensure that the machine can be properly arrested temporarily.
When the switching is desired during the execution of a series of the programmed operations, the operator cannot know the content of a next step to be performed within the control program until the step is actually executed to cause the machine operation to be resumed. For this reason, the operator wonders at all times whether the control program sequence coincides with the actual operating sequence controlled by the program.